1. Field of the Invention
The present invention relates in general to aircraft, and more particularly to aircraft escape systems. Most specifically, the present invention relates to protecting those personnel and/or equipment in other ejection seats remaining on board an aircraft from the thermal and blast effects of the ejection procedure during a multi-personel ejection procedure.
2. Description of the Prior Art
As is well known, emergencies sometimes occur during the operation of high speed high performance military aircraft. These emergencies sometimes are serious enough to require the inflight evacuation of the personnel from the aircraft. Therefore, most modern high performance military aircraft have systems for ejecting the aircraft personnel from an aircraft which may be moving at a rapid speed and may also be out of control and experiencing pitch, yaw and/or roll conditions. Under some emergency conditions, it is imperative that the personnel be removed quickly from the vicinity of an aircraft. However, it is equally important for the personnel to be able to effeciently and reliably operate the aircraft under normal conditions and to manually evacuate the aircraft if necessary. Therefore, while modern high performance aircraft must have systems for rapidly removing personnel from the aircraft, such systems must not interfere with the crew's ability to operate, or to manually exit from that aircraft.
Most aircraft personnel ejection systems include a seat which has a rocket propulsion system for rapidly removing the seat from the aircraft. The seat is movably mounted on rails for guiding the seat out of the aircraft during the ejection procedure. These seats also generally include a system for controlling seat movement after it has been separated from the aircraft mounted guide rails whereby the seat and its occupant can be moved, in a controlled manner, to enhance altitude gain and body orientation. Such control systems include means for sensing seat pitch, yaw and roll and often also include rockets for correcting unwanted seat movement. The seat can undergo pitch, yaw or roll or a complex combination of such movements, and the seat control systems must be able to react rapidly to control such movements. Furthermore, seat flight conditions may be influenced by movements of flight of the aircraft prior to and during separation of the seat from the aircraft. For example, if the aircraft is experiencing severe roll at the moment of seat separation, the seat may be correspondingly tipped with the bottom thereof moving toward one side or the other of the aircraft depending on the direction of the aircraft roll. The seat control system therefore will attempt to correct such seat tipping. In seat stabilization systems employing rockets, this is accomplished by redirecting the thrust orientation of a rocket or by firing appropriate rockets.
Such seat tipping, when combined with other conditions, may cause a seat control rocket to fire directly at the aircraft. Such a firing may cause the high temperature, high velocity rocket exhaust gases to impinge directly on the aircraft. In many situations, this is not a problem. However as will be discussed below, there has been one occurrence in which an unusual combination of events caused this possibility to be entirely unacceptable.
Many modern aircraft include an arrangement of seats to accommodate multiple crewmembers, that is, the seats are positioned adjacent to each other, either in a side-by-side or in a tandem (fore-and-aft) configuration. Therefore, the above-discussed situation in which the seat rocket exhaust gases impinge directly onto the aircraft proved to be entirely unacceptable in a procedure in which an aircraft crewmember located in a side-adjacent seat was still on board the aircraft during the ejection of the adjacent seats and had the rocket exhaust gases from the ejecting seat impinged directly on him.
There are several possible ways to prevent a reoccurrence of the above-mentiontioned unacceptable possibility. One way is to eliminate the ability of an individual crewmember to initiate self-ejection whereby both seats of a multiple seat combination are controlled by one of the seats to eject simultaneously when the control seat is ejected. However, this may endanger the crewmember in the controlled seat if the occupant of the controlling seat fails to initiate ejection procedures. Furthermore, if the system in the controlling seat fails, both seat occupants are in danger. A variation of this method would include a seat ejection system in which both seats are ejected essentially simultaneously if either seat is ejected. However, this reverses the above situation and may result in unnecessary ejections with their attendant risks in the event a crewmember panics and initiates ejection prematurely or unnecessarily. This latter condition may place a pilot under the control of a crewmember, which under many conditions is not desirable.
Another way to prevent occurrence of an unacceptable situation in which rocket exhaust from an ejecting seat impinges on personnel in the aircraft is to delay firing of the ejection seat rockets for a predetermined time after separation from the aircraft. However, during this delay, the seat is not being actively propelled or controlled and may fail to gain sufficient height above aircraft and/or terrain and, in addition may become unstable enough where it cannot be brought sufficiently under control for proper parachute deployment. Introduction of such delays also entails a reduction in rocket ignition reliability. Such conditions are not acceptable.
Furthermore, adding means which change the existing aircraft seat ejection systems or procedures must be tested and proved effective before modifying aircraft and aircraft specifications. Such a requirement may be costly and time consuming.
Therefore, modifying aircraft ejection seats, seat ejection sequencing or procedures do not appear to be viable ways of preventing a reoccurrence of a situation in which rocket exhaust gases from an ejecting seat of an aircraft multiple seat configuration impinged on personnel in the other seat still aboard the aircraft.
Accordingly, it will be necessary to provide equipment which permits either seat of such a multiple seat combination to eject as in the present situation, but which automatically protects onboard personnel during ejection of the other seat. Such equipment must be simple to reduce the possibility of malfunctioning, and to permit rapid and expeditious testing and implementation of the equipment into aircraft specifications. The equipment should also be amenable to retrofit procedures so that existing aircraft can be expeditiously modified.
Furthermore, to obviate the problems discussed above with regard to ejection sequencing procedures, the equipment should be capable of being actuated by either seat independently of the other seat. In this manner, neither seat occupant's protection is dependent upon or adversely influenced by the operation of, or lack of operation of, the other seat. Nor should the equipment interfere with the operation of the seat being ejected during the ejection procedure.
Yet a further requirement for such protection equipment is that it should not interfere with the operation of the aircraft. For example, the equipment cannot form an impediment to verbal or visual communication between the personnel in the aircraft or with the actual control of the aircraft during aircraft operation. Furthermore, this equipment should not create a clausterphobic situation in the aircraft or interfere in any way with manual egress should such procedure become necessary. Therefore, the the equipment must be designed to be located well out of the way during normal aircraft operation, yet be automatically, quickly and reliably deployed during an ejection procedure.
Prior art ejection systems have focused on protecting the occupant of the ejecting seat itself from the ejection environment external to the aircraft, see, e.g., U.S. Pat. Nos. 2,579,683, 2,965,335 and 3,630,472; or to preventing one ejected seat from physically interfering with another ejected seat, see e.g., U.S. Pat. Nos. 3,606,221, 3,648,955 and 4,225,101. However, the known prior art has not approached the problem of protecting personnel remaining onboard an aircraft against the exhaust gases of rockets of a seat which has been ejected from that aircraft.